Liquid pressure control apparatus



Nov. 7, 1939. c. R. HANNA LIQUID PRESSURE CONTROL APPARATUS Filed Aug.25, 1938 2 Sheets-Sheet l m W Rm gek. M w ma 1T a 3 NH k e r ER m w w mnW W/W D/ wwf 0 ,w e J 2/3 u .nm m fl. U C 0/ w M J M a f 0 C MW 0/ 4. .mA@ mC 7 A w A A 0 0 0 0 E w w .w w 2 .m mwf/f m MWWV ATTORNEY Nov. 7,1939. c. R. HANNA 2,179.292

` LIQUID PRESSURE CONTROL APPARATUS Filed Aug. 25, 1938 2 Sheets-Sheet 2WITNESSES: INVENTOR ATTORN EY @45,1 MM, 60mn R Hama.

W /Mm ya Patented Nov. 7, 1939 lcE f p LIQUID PRESSURE ooN'rnoLAPPARATUS,

` Clinton B. Hanna, Wilkinsburg, Pa., assigner to i WestinghouseElectric & Manufacturing Coml many, East Pittsburgh, Pa., a corporationo! 1 Pennsylvania *Application August 25,1938, semina. starci l! pcomms. (ci. 1lis-sin My `inventionrelates to valves, moreparticularly tovalves for controlling thefiow oi. liquid from a high-pressure chamberto a chamber of" lower pressure;

The `detalls of my valves have been disclosed and for a particularequipment have been claimed in my'Patent No. 2,140,359, issued on anapplication filed December 14, 1934, entitled'Valve-arrangement`1of`inertia shock `absorbers and oi which patentlthis application isf acontinuation inpart.` i In controlling` the flow `oi.' liquid from a.relatively high-pressure compression chamber to a chamber of lesserpressure, `it is frequently desirable ,to control the liquid ilow byvalves of minimum sizeand which valve or `valves may readily becontrolled. i

One broad object `of `my invention lstocontrol the flow of liquid from a`compression cham- `:i0 ber as a given function oftheliquidfdisplacement in the compression chamber. i Another object of`myinvcntion is toprov'lde for resisting .the owlof liquid in conduitmeans, interconnecting a liquid compression chamber with a chamber oflower liquid compression, `by a force substantially proportional to therate oi change of the volume oi the compression chamber. l l Anotherobjectof myinvention is to control the pressure of a liquid in achamber, which liquid is subject to variable pressure, in proportion tothe volume velocity of the liquid flow through aconduit connectedito`drain liquiditrom the chamber. 1 i i Still other `objects `andadvantages of my inventonwill be readily recognized and a fullerunderstandingof my invention will be had `from a study of the followingspecification `and the accompanying drawings, inV which:

o Figure 1 is a longitudinal `sectional view ci my nventiom; t v i i iFig. 2 is a view of my inventionon section line II--II of Fig; 1; Fig. 3`is a sectional view of an ine `is. `controlled hydraulic shock`absorber providedwith my novel pressure control valve and oriiice`arrangement; and" i Fig. 4" sho-ws graphically the operatingcharacteristics oi.' my invention. 5o Referring to Fig. 1, it will benoted that I show e conduit l leading `from a chamber or reservoir 2,see Fig. 3, of relatively high liquid-pressure to a chamber 3 ofrelatively low liquid pressure. Disposed in the conduit is a valve Ihaving a conical valve seat engaging portion .'i` which coacts with thevalve seat 6"`to completely` close the conduitwhen there is no pressuredierence between `the liquid in the two chambers 2 and l. This-valve hasa"s1eeve portion l provided with one or more parallel sided slits 8. Itseveral slits are used, they are preferably symmetrically disposedaround the sleeve portion 1. as shown in Fig. 2.

The valve l is provided with a spring holding or guiding stud Q and aspring Il is disposed be- 5 tween the rear end of the conical portion Iand a spring positioning nut Il. The spring is disposed between thesetwo mentioned elements so as to be under substantially no compressionwhen the valve 4 is closed. At zero pressure on the 10 valve l, therewill, oi' course. be zero opening of the valve, but the area o! theopening through the slits 8 will be directly proportionall to the valvedeflection. In Fig. 1 the valve 4 `is shown open as if liquid were being`forced through the 15 conduit I and the spring Il is under compression.As shown lnFig. 3, spring Il is under no compression. p l The nut' Ildisposed at the right hand end oi the `spring lll is provided with athin-walled go orifice l2. The area of this orifice mayhave any selectedvalue by `simply selecting from a plurality of nuts having thin-walledoriiices of different.` diameters the particular that is desired." By a`proper combination, `or selection or the valve `4. of the desired slitss, of the spring 25 I0 and `of theorillce l2, the resisting force to amovement of the liquid through the conduit I may be made directlyproportional to the' volume velocity'ol the liquid displaced fromchamber 2,

maris, theuquid pressure in chamber z may be 0i made directly`proportional to the quantity of liquid flowing in conduit l ina giventime. This means, referring to Fig. 3. that the pressure in thecompression chamber 2 may be made directly proportional to the velocity`of movement ofthe piston I3 or, in other words, the shock-absorbing iaction. f

That the foregoing theory of operation istrue may be readily understoodfrom `the renewing i. analysis: o

. It may be readily shown that the pressure in chamber 2 `is directlyproportional tothe area ofthe opening at the slits l and that the pressure is also proportional to the two thirds power of the volumetricvelocity, or displacement of the liquid. l i

e1) reinem-ca of "the orme-c la;

` The mass of the liquid used. namclyioil,=tAX where =the specii'lcgravity of the oil and X== thc distance in a straight line the end of astream 60 of oil would move if it maintained its sectional area A and.did not change its direction of movement.

Another expression for energy is XPA where P is the liquid pressure, orforce, acting on the area of the oriiice I2. Equating,

and of the spring I0, A can; for the operating range, be madeproportional to P, that is substituting 10) in (7) V,

#Wma

Peggie 3 P=Kv2/3, that is, P is--proportional to vw,

Wh'ere K is the. proportionality constant.

'I'he pressure drop through the thin walled aperture or orifice*y I2 isproportional to the square of uthe velocity in accordance with thefollowing law:

P'= 1/26122, see Equation 7; therefore P is proportional to v2. l

By combining the pressure drop through the valve 4 and through the thinwalled orifice I2 and that through the fixed orifice 54, thesubstantially straight line proportionality between reaction pressure orresisting force and the volume velocity oi'y the displaced liquid may beestablished, as shown in the graph in Fig. 4.

Since the pressuredrop through the valve 4 will vary as the 2/3 power ofthe volume velocity, and the pressure drop through the thin walledoriiice I2 will vary as the square of the velocity, the two pressureswill add to establish a total pressure drop that will be substantiallydirectly proportional to the displacement of the liquid from thecompression chamber, for the larger values of pressure within theoperating range. The small oriiice 54 provides a bypass for the controlvalves 4 and orifice I2 which serves to reduce the pressure drops pastthe valve and the orifice in such manner as to equalize the straightline relationship between pressure and velocity at the lower values ofpressure. 'Ihe curves of Fig. 4 show this,

As shown in Fig. 4, the curve I5 represents the relation between thepressure and the volumetric displacement of volume velocity of the fluiddisplaced from the compression chamber, which is the relationshipP=V2/3. The curve I6 represents the pressure drop through the fixed oricI2 which is represented by P=KV2. The curve I'I represents the combineddrop of curves I5-and I6 whereas curve I8 represents the combinedpressure drop when using the bypass orice 54. It will be observed thatby properly 'comblning the pressures represented by the curves I5, I6and the eifect of by-pass 54, a combined u pressure represented by thesubstantially straight line I 8 for the desired operating range will beestablished as a reaction pressure or resisting force set up by theshock absorber.

In operation when the pressure differential rises between the twochambers 2 and 3, liquid will begin to flow. At the initial stages ofany considerable liquid ow past valve 4 the spring II) alone resistsliquid ow but as soon as the ow takes on any proportions at all, apressure is built up in the region occupied by the spring I0, whichpressure also acts on valve 4. The size of the orifice I2 is thus ofimportance in controlling fiuid flow. The nut is, therefore, designed tobe removable so that nuts having various size openings may be inserted.Different weight springs'may also be inserted to give differentproportional controls. This is readily apparent from the showing in Fig.3 where two different fluid flow passages are shown. The spring may begiven a very slight initial compression to thus in nowise iniiuenceiiuid iiow for low pressures but for such low pressures leave thecontrol entirely to orice 54.

Fig. 3 shows my invention applied to a shock absorber such as shown inFig. 5, of the oopending application hereinbefore mentioned, except thatthe inertia control is not shown and the apparatus absorbs shocks onlyon the rebound. The casing may be considered connected to the sprungmass of a vehicle whereas the lever arm may be considered connected tothe unsprung mass, as the axle, of the vehicle.

When the wheels of the vehicle strike a bump' in the road, lever arm 20will first be moved quite freely in a counter-clockwise direction.Liquid will freely pass into the compression chamber 2. As soon as thevehicle body is accelerated vertically upward, the piston moves towardthe left, that'is, the arm 20. begins to move clockwise Valve 2| closesand the liquid in thecompression chamber is forced through the conduitI, and the' movement of the piston is resisted by a force substantiallydirectly proportional to the volumetric velocity of the liquid flowingthrough conduit,

If the rate oi movement of piston I3 is too high so that one valve andoriiice arrangement does not suiiice, then both valves shown, open butthe valve and oriiice selection for the second valve 22, spring 23 andorifice 24 may nevertheless be such as vto effect a control proportionalto the velocity of movement of piston toward the left.

I am, of course aware that others, particularly after having had anopportunity to become versed with thel teachings of my invention, candevise similar apparatus for accomplishing the same and similar results.I, therefore, do not wish to be limited by the speciiic showings hereinmade and particularly do not wish to be limited to the particularapparatus with which my invention is shown but I wish to be limited onlyby the appended claims and such prior art asmay be pertinent.

I claim as my invention:

l. A valve system for a hydraulic motiondamping device, comprising avalve that is spring loaded .with zero initial pressure and that isdesigned to provide an area of opening proportional to the pressure ofthe fluid tending to open the valve, and a thin-walled orifice in serieswith the valve to establish a cooperative combined effect upon thehydraulic fluid that will render the pressure responsive to the uiddisplacement.

2. In a valve system for hydraulically damping the movement of anoscillatable member, the

-duit consisting',` of a spring loaded valve with substantially zeroinitial pressure loading and designed to present an openinglproportional to ythe iluid pressure, and a narrow-walled oriiice in thepassage in series with the valve.

3. In a valve system for hydraulically damping the movement of 'anoscillatable member, the combination with al pressure chamber containinga uid, in which said oscillatable member is movable as apressure-developing member, of a conduit leading from the chamber toconduct the liquid therefrom under the developed pressure, and valvemeans in said conduit consisting of a spring loaded valve designed topresentan opening whose area is proportional to the pressure of thefluid, and of a back-up narrow walled orifice in the conduit in serieswith the valve.

4. A valve system for hydraulically damping the movement of anoscillatable member, comprising a closed pressure chamber containing afluid and a movable member therein mechaniccally connected to the memberto be damped, a conduit leading from `the chamber, a ilrst controldevice in the conduit consisting of a spring biased sleeve valve with aslot of constant width in the sleeve portion and under substantiallyzero initial spring force to develop a pressure proportional to thetwo-thirds power of the fluid velocity, and a second control device inthe conduit consisting of a lthin wall having an orifice disposed to bein series with the first valve device to add a pressure to the iluidthat is proportional to the square of the iluid velocity, whereby i theresulting iluid pressure is causedto be nearly a straight line` functionof the iluid volumetric velocity.

5. In a hydraulic damping system for a movable member, a compressionchamber vcontaining a iluid, a piston in the chamber and adapted to beconnected to the movable member, a conduit leading. from the chamber toconduct the iluid from the chamber, and means in the conduit forestablishing a reaction pressure against the fluid proportional to thedisplaced fluid velocity, said means including a valve means forestablishing a pressure proportional to the two-thirds power of theiiuid velocity, and a thin-wall orice in series with the valve toestablish a pressure proportional to the square of the fluid velocity,whereby the combined pressures will combine to establish a substantiallystraight line function of the fluid velocity.

6. A' hydraulic shock absorber comprising a container embodying acompression chamber, a movable piston therein, and adapted to bemechanically connected to an external member whose motion is to bedamped, a conduit con nected to the chamber to conduct the displacedfluid from the chamber, and means in the conduit for establishingreaction pressure against the displaced iluld and proportional to thedisplaced iiuid velocity, said means including, as a ilrst control unit,a self-adjustable spring-loaded valve for establishing a pressureproportional to a less-thanunity power of the nuid velocity. andincluding. as a second control unit, an element having an orifice inseries with the valve to establish a pressure which, when added to thepressure established by the valve, will make the total reactionpressure, against the' displaced fluid, a substantially straight linefunction of the uid velocity.

7. In a hydraulic braking device for la movable member, means fordeveloping a reaction braking pressure substantially directlyproportional to the velocity of the movable member, comprising a body offluid disposed to be moved by the movable member, a conduit to conductthe fluid, a spring-loaded valve in the conduit' deslgnedto provide apassage opening for ,the fluid whose area will be proportional tothefiuid pressure, and an element in series relation with the valve toprovide a xed oriiice for the' displaced fluid to pass through thedimension oi the orince being vmade such as to provide a pressure dropwhich,

when added to the pressure drop through -the valve, will establish thedesired direct relationship of pressure to velocity.

8. In a hydraulic damping system for a pair of relatively movablemembers, a compression chamber containing a iiuid in one of the movablemembers, a piston in the chamber and adapted to be connected to theother movable member, whereby relative movement of the members altersthe volume of the compression chamber, a conduit leading from thechamber for conducting iluid from the chamber when the piston is movedto decrease the volume of the compression chamber, and uid owrestricting means in said conduit adapted to restrict the flow of fluidthrough the conduit so as to maintain the pressure in the compressionchamber in proportion to the change of volume of the compressionchamber.

9. A. valve system for a hydraulic motiondampingdevice, comprising avalve that is spring loaded with substantially zero initial pressure andthat is designed to 'provide an area of opening proportional to thepressure of the fluid acting to open the valve, and further iluid flowrestricting means coacting with said valve and adapted to establish acooperative combined effect upon the hydraulic fluid that will renderthe pressure proportional to the iiuid displacement.

CLINIDN R. HANNA.

